1. Field of the Invention
The present invention relates to a light scanning apparatus molded out of fiber-reinforced resin and an image forming apparatus including the light scanning apparatus.
2. Description of the Related Art
Conventionally, in an electrophotographic image forming apparatus, a light scanning apparatus using a housing molded out of fiber-reinforced resin has been often used.
The light scanning apparatus includes a deflector configured to deflect a light beam emitted from a light source so that the light beam may scan a surface to be scanned. The deflector includes a polygonal reflection member having a plurality of reflection surfaces configured to reflect the light beam, a motor configured to rotate the reflection member, and a drive board provided with an integrated circuit configured to drive the motor. The motor and the integrated circuit generate heat by electric power supplied thereto. A housing deforms by the heat generated from the motor and the integrated circuit. The thermal deformation of the housing changes the positions of a mirror and a lens supported by the housing. Thus, color misregistration may occur in a color image forming apparatus.
A mean coefficient of linear thermal expansion in a direction along a fiber orientation of the fiber-reinforced resin of the housing is smaller than a mean coefficient of linear thermal expansion in a direction not along the fiber orientation. The amount of thermal deformation of the housing therefore depends on the fiber orientation. The fiber orientation of the housing molded out of fiber-reinforced resin depends on a molding method of the housing. That is, the housing has an easy-to-deform direction and a hard-to-deform direction.
Japanese Patent Application Laid-Open No. 2008-168622 discloses a technology of controlling the fiber orientation of a member molded out of fiber-reinforced resin to reduce the amount of thermal deformation in an apparatus other than the light scanning apparatus. It is an object of Japanese Patent Application Laid-Open No. 2008-168622 to prevent a heating member bonded to the member molded out of fiber-reinforced resin from separating or being broken by the difference in the amount of thermal deformation between the member molded out of fiber-reinforced resin and the heating member. In order to achieve the object, in Japanese Patent Application Laid-Open No. 2008-168622, the fiber orientations are uniformly aligned along a direction in which the amount of thermal deformation of the member molded out of fiber-reinforced resin is intended to be suppressed. In this manner, in the direction in which the amount of thermal deformation is to be suppressed, the difference in the mean coefficient of linear thermal expansion between the member molded out of fiber-reinforced resin and the heating member is reduced, thereby reducing the difference in the amount of thermal deformation.
In the light scanning apparatus, the housing is provided with a rib configured to ensure the rigidity of the housing. Heat generated from a heat generating source produces a temperature difference between a bottom member of the housing and the rib molded out of fiber-reinforced resin integrally with the bottom member of the housing. The temperature difference may be responsible for distortion of the housing.
In addition, simply aligning the fiber orientations of the rib and the bottom member in one direction may result in an increase in the amount of thermal deformation of the housing.